Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 Apollo 1/28/85; site apollo.uucp
Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxb!mhuxn!mhuxm!mhuxj!houxm!whuxlm!harpo!decvax!wanginst!apollo!tweed
From: tweed@apollo.uucp ()
Newsgroups: net.audio
Subject: Re: CD Reflections - 44.1k?
Message-ID: <24747339.298c@apollo.uucp>
Date: Tue, 29-Jan-85 11:11:17 EST
Article-I.D.: apollo.24747339.298c
Posted: Tue Jan 29 11:11:17 1985
Date-Received: Thu, 31-Jan-85 01:21:41 EST
References: <15100001@hpfcmp.UUCP> <3411@mit-eddie.UUCP> <1420@hplabs.UUCP> <755@clyde.UUCP> <258@petrus.UUCP>
Organization: Apollo Computer, Chelmsford, Mass.
Lines: 47

ced at
intervals of the sampling frequency above the baseband carrier (0 Hz).  Any
aliasing you hear in a digital reproduction occured in the manufacturer's lab,
not in the CD player -- and oversampling can't help it at all.

Oversampling *will* help in the following situation:
   Suppose there is a (sine-wave) signal at 20000 Hz.  (Bells and other metallic
instruments can produce strong signals in this range.)  In the reconstructed
waveform, there will also be a signal at 44100 - 20000 = 24100 Hz, which is
not harmonically related to the original signal (the ear is much less sensitive
to harmonic distortion than to other forms).  If your system can reproduce this
signal, and you are capable of hearing it, you will find it objectionable.
Furthermore, if your system is subject to intermodulation distortion (and most
power amplifiers' distortion figures go way up in this frequency range), a signal
will be produced at 24100 - 20000 = 4100 Hz, which is *certainly* hearable, and
again, not harmonically related.  As someone mentioned, oversampling can help
suppress that 24100 Hz image by as much as 50 db (before filtering), which will
make it much less likely to show up the flaws in the rest of your reproduction
system. 

                                                         -- Dave Tweed
                                                         ...!apollo!tweed